Zirconium tetrachloride production



June 14, 1960 J. w. v\|-\DERsEl\J zmcoNIuM TETRACHLORIDE PRODUCTIONFiled sept. 12, 1957 lPatented June 14, 1960 ZIRCONIUM TETRACHLORIDEPRODUCTION .lohn W.. Andersen, Dayton, Ohio, assignor to Monsantoghmlcal Company, St. Louis, Mo., a corporation of e aware Filed Sept.12, 1957, Ser. No. 683,619

5 Claims. (Cl. 23-87) This invention relates to a process for producingzirconium tetrachloride. More specically, it relates to a process forproducing zirconium tetrachloride by the chlorination of nely dividedsolid zirconium-bearing materials in iiuidized beds.

The formation of zirconium tetrachloride by the reaction of a gaseouschlorinating agent with a mixture of solid zirconium oxide-bearingmaterials and carbon has been carried out in the past. However, theutilization of this reaction in a large scale continuous productionprocess has posed many technical di'iculties which, prior to the presentinvention, have not been satisfactorily overcome. v Y l Y The iiuidizedbed chlorination of simple mechanical mixtures of iinely groundzirconium oxide and carbon can be carried out to some extent, but thereare various problems associated with this technique which make it verydi'lcult to carry out successfully. Por example, unless the solids arevery nely ground in order to expose large surface areas thereof, therate of chemical reaction is very slow and the zirconium extractionefiiciency is poor. On the other hand, when the solids are very nelyground there is a strong tendency for the solid feed materials, as wellas the resulting lash, to be carried out of the reactorwwith theoverhead gases. Also, with very small uidized solid particles there is amarked tendency lfor the solids to stick to the reactor Walls, lumptogether in the reactor bed and contribute generally to diculties inmaintaining the solid bed in a uniform state of iudization. Theforegoing diiiculties, as well as numerous others, are overcome by thepresent process as described hereinbelow. .v

According to the present invention a uidized chlorination of zirconiumoxide-bearing materials can be very readily carried out by chlorinatingat an elevated temperature a solid mixture of zirconium oxide andcarbon, said oxide and said carbon being very nely ground 1 andagglomerated into a particulate granular mass with a binding agent whichwill not decompose at the elevated chlorination temperatures.

The present process is applicable tonumerous different forms ofzirconium oxide and varieties of ores containing zirconium. For example,one suitable source of zirconium is zirconium dioxide, which occursnaturally in such minerals as baddeleyite. Another highly suitablesource of zirconium is zircon (a zirconium silicate which can berepresented as ZrO2.SiO2), which occurs naturally in various pegmatites.Other common sources of zirconium are zirconiferous beach sands orconcentrates thereof, such as the tailings remaining after the recoveryof titanium dioxide from ilmenite, rutile, monazite and similartitaniferous minerals. From the foregoing it will be readily recognizedthat the term zirconium oxide as used herein refers to any of theforegoing or similar ores and concentrates from which zirconium can berecovered by chlorination in the presence of a carbonaceous reducingagent.

In practicing the presentinvention the zirconium oxide is linely ground(for example, to about minus 200 mesh, and preferably 80% minus 325mesh) and intimately mixed with a carbonaceous reducing agent which hasalso been nely ground (for example, to about 80% minus mesh, preferably80% minus 200 mesh). Preferred examples of carbonaceous reducing agentsare channel black and petroleum coke, but less pure forms of carbon suchas ordinary coke, hard coal, charcoal, etc. can be utilized with goodresults under manycircumstances. The` quantity ofV carbon used inthemixture with zirconium oxide must be at least the stoichiometricamount required to convert all of the oxygen in the zirconiumoxide-bearing source to the particular ratio of carbon monoxide andcarbon dioxide which will be produced under the conditions at which thechlorination reaction is to be carried out. The mixture of carbonmonoxide and carbon dioxide produced during -the chlorination willgenerally be in the neighborhood of 1 mole of carbon monoxide to 4 molesof carbon dioxide, which is just about the` reverse, of what would havebeen predicted from thermodynamic considerations. Consequently `it isrecommended that the amount of carbon used in the mixture withzirconium.oxid'e be a least the amount stoichiometrically requiredto'cmivert all of the oxygen in the zirconium-bearing material to carbonmonoxide, and :preferably 1.5 ,timesi that amount. I The ,foregoing nelyground solids are intimately intermixed with a binding agent (generallyutilized as an aqueous solution) and the resulting mixture isgranulatedas for example, by passing through a granulating screen.Suitable binding agents for forming the aforesaid granules are any suchagents which will not allow substantial disintegration of the granulesat the temperatures at which they are chlorinated.` Because suchtemperatures are relatively vhigh (for example, 700 C. and higher)suitable binding agents-'will generally fall within the class of glassy,inorganic, high melting point materials. Examples of particularlysuitable binding agents are various alkali metal silicates, andespecially the diand tetra silicates or mixtures thereof; various4inorganic phosphates such as sodium, potassium, aluminum, etc. andother metal ortho, meta, pyro, and polyphosphates; hydroxides, such assodium and potassium .hydroxidesg and numerous others.

The concentration of the bindingagent utilized (based upon total dryWeight of solids in the agglomerated granules) will'generally fallbetween about 5 or 6% and about 12 or 15% by weight. Y v

v-The `foregoing granulating procedure should be designed andcontrolledso as to produce a granulated solid feed having particle sizesfalling between 8 and 20,0

mesh V(U .S. Standard sieve sizes). The particle size distribution ofthe bulk granular feed should generally be such that 70 weight percentof said granules will be between l8 and 140 mesh, and preferably suchthat 80 weight percent thereof will be between 2O and 100 mesh.

The above-described granulated solids are then ilufidized in anyupwardly flowing stream of chlorinating l gas in accordance withwell-known principles of uidization technology. The chlorinating gas ispreferably elemental chlorine, or mixtures of chlorine with othernon-chlorinating gases such as carbon monoxide, carbon dioxide,nitrogen, etc. in which the chlorine comprises an appreciableconcentration (for example, greater than 25 mole percent and preferablygreater than 50 mole percent). Other chlorinating gases such asphosgene, carbon tetrachloride, hydrogen chloride, etc. are also useful,especially when used in conjunction with chlorine. In order for thechlorinating gases to maiutain the aforesaid granular solids in asatisfactory state 'of iluidization, the gases will generally be passedupwardanimas lyk-through the -bed of solids at a superficial velocity Aranging between about 0.5 and .about 1.0 foot per second. Reactionbetween the granular solids and lchlorinating gases Vwill proceedreadily at elevated temperatures, for Y example, temperatures betweenabout 7009. and-,about 000 `C'. ,and :preferably .betweennabou'tV V800'C.' and f about 9.00"V C. Y .In -order tonaake the. process thermallyselfsustaining (takinginto account'theA rates-of reaction aswellasfnormalheat losses from commercially feasible reactors.) it vwillgenerally be' desirableito Preheat one orfboth-of'thereactantlmaterialsY ('i.e.,-.the solid granular feedV .and/or thechlorinating gas)-'-th.=. degreev lof prev`depending atleast in .partupon theparticular sonrc'e-ofl-zirconium being chlorinated; Forexample,

utilizing 'relatively pure VZircon fas a raw `material, the. reactantlpreferablylbe preheated to approximately the ksame temperature as thereaction temperature; when Y Vusing-"zirconia,Y somewhatlowerfeg. 100 C.to `150'" C.

Example is introduced through line and passes upwardly through theiluidized bed reactor. The uidized bed is maintained with a depth ofabout 9 feets About 80 pounds of chlorine is introduced per 100 poundsof solid feed introduced. The coarse spent (extracted) solids areallowedto overflow through line 26 into the coarse ash collector 27. rTheoff-gases from theiiuidized reactor are withdrawn overhead throughVVline 28 and led in to rthe cyclone separator 29. `These Ygases contain(in -additionto ZrCh, SClc .TiCln C12., ,Ii/C5902, and.0) ,sma1lamounts'of 'Feile and Ysus'nelldtd "na, ash. ln'order vto prevent theFe/Cls fromtoondensing with and contaminating th ZIEL gaseous hydrogenis introduced through line 30 to convert the Fel3 to FeCl2. The cycloneseparator eisirnaintained iat a temperature of about 400 C. in order tocondense the FeCl2 without precipitating ZrCh.V The remaining gases,substantially.

free of condensed solids, are withdrawn from the cycloneseparator'throu'gh line 131 and'introduced into thescraped condenser 32-which is ymaintained at vaternperature of about 200 C iin order tolprecipitatey ZrCl4 without conlensing TiCl4, .SiClLb etc. The condensedZrCl is scraped Y from the condenser walls by rotatingscrew 33 and fallsfrelan'vely pure Zircon concentrate (analyzing ZrOg,Y Y

'64. percent; Hf02, 1.0 wt. percent; SiO2, 3.1.5. wt. percent; VTiQg,C1303, -rnonazite, etc.,r 3.5, wt. percent) Y is.crushe'dfina cone-crusher ilgdrie'd ina dryer 12, and

milled in a continuous ball mill 13 (including a closed circuit'airclassifier) to give a ground product of `which 100% .will'pass a 140Vmesh screen, 98 weight percent will pass a-200 mesh screen, and '87%will passA a 325 mesh-screen.V Likewise, petroleum coke is crushed incone Crusher 14, dried in dryer 1S, and milled in ball mill 16 YYto'give aV product of which 100% will pass a 140 mesh screen, 98% `willpassa 200 mesh screen, and 69% will Y Vpass a 325 mesh screen. f

Seventy-nineand Vsix-tenths parts by Weight of the zircon, 12.4`Vpar'ts'by weight of the petroleum coke, and Y 21.2. parts by weight ofan aqueous sodium silicate solut-ion (containing 8 parts by weight ofsodium silicate, SiO2/N'a2O=3.22) Vare all mulled together inanedgerunner pan mill 17 until (about one hour) a moist easilypackedmix-ture is ormm. This moist mixture-.Sis continuously fed through ascrewconveyor 18 to a granulator VA-19'iitted with -a 20 meshgranulating screen. The f resulting -granulesare passed underan infraredradia- Ytion heater'rl and Aheated-t04 'a temperature betweenabout 200and about 300 Cqto reduce the water content of the' granules to below`0.5 weight percent; AThe dried granules `are cooled to about 100? C.yand fed to a 2-decked sieve 21 upon which they are separated into?three different fractions: (l) particles which do'not pass f'throu'gh -a16 -mesh screen; (2) particles which pass through-2116 mesh-screen'butwhich -do not pass-through a 100 meshscreen; and (3)'particles Whichpassthrough a 100'mesh screen. The over-size material is passed to a coarsevroll Y crusher `22 (roll setting kof about 0.0257) and recycled Y totheV Z-decked sieve.

either discarded lor recycled to theY edge-runner-pan mill 17, (Iftherfmes are recycledY toY the pan-mill, a propor- The minus 100 meshmaterial is *tionatelyglarger amount of silicate( binder solutionmustalso be added into the pan mill.) Y Y fl'heresulting granulated solidfeed (having a particle size distribution such that 100% pass through al'mesh screen, Y95 Yweight percent pass through a 20 mesh screen,'/SWeight percent pass Ythrough a 35 mesh screen, and only; 0.5 weightpercent pass through a 140 meshscreen) Yisplace'd in. a preheater 23.from which Vit isV continuously introduced into a Yfluidized bedreactor 24. In the pre- V,heater .the solids are heated toatemperature'ofabout ,850 YC. The uidizedbed is `also maintained atAabout 50? Q C. i Chlorine gas, also preheatedto about 850 C.,

'into the retention -bin 34 from which it is removedthrough line 35. Theremaining uncondensed gases vare withdrawn overhead through line 36.These gases can be further processed to recover TiCl4, SiCl4, unreactedClz, etc.

in myeopendng application Serial No. 454,778, nled 'September 8, 1954,there is Adisclosed and claimed a method for producing titaniumtetrachloride by -a process somewhat relatedfto'the process of thisinvention.

What is claimed is: Y'

l. A method for continuou'sfsteady-state production of zirconiumtetrachloride 'by' the chlorination of solid bonded agglomerates of:finely divided zirconium oxidebearing material of which Vat least V80%will pass a 200- inesh screen,` and iinelyfdvided solid carbonaceousreducingagent of Which/aty least 80% will pass a i40rnesh screen, theamount of 'carbonaceous reducing agent in said -agglomerates VbeingVs'toichiornetrically Vsnflicient to convert all of the ,Oxygenlin saidvzirconium oxide-bearing Vmaterial Vto the carbonV monoxide/carbondioxide mixture; produced under the existing chlorination conditions,

saidA finely divided` zirconium oxide-bearing material and saidjnelydivided vcarbonaceous*rerhxcing agent being bonded 'together with aninorganic `chemical lbinder of suicientf strength tolprevent`substantial physical degradagaseous ichlorine andthe.aforesaidf'agglomerates in a udi'zed bed .reactionzone maintained "at Latemperature :betwenahout 700.Cand .about 1000 the upward velocity of.thegas being suiicie'nt tomaintain .said solids i `it! .3; turbulentuidiled siate..

2. vThe method of claiml 1 in which-.the reaction zone temperaturevis-maintainedV between about 800 C. and about. 900l C.. .t

3. The method .of claim l in which the reaction zone temperatureisfmin'tained .between `about 800 C., and --about 900"V C., and theparticle size .distribution of the solid agglomeratessisl such that atleast weight percent thereof are between'lS and l40-mesh.

4. TheY method of Vclaim l 1n which Vthe reaction Vzone temperature "ismaintained'between'about 800- VC.. and about 900'7C. andthe I particlesize distribution of the solid agglomerates is such that atleast weightpercent thereof; areV betweenrZiO. and yg-mesh.

V5. yThe method o,f :lairr iA Vl in which the inorganic ,chemical binderis .a Yrrerulnerselected `from thergroup consisting of sodium-silicatesand sodium hydroxide.

(Retrencesonifollowis Page) i Y g 5 References Cited in the le of thispatent 763,308 UNITED STATES PATENTS 2,608,464 Aagaard et al Aug. 26,1952 1,123,603

FOREIGN PATENTS 5 466,705 Great Britain June 2, 1937 689,012 GreatBritain Mar. 18, 1953 6 Great Britain Dec. 12, 1956 Great Britain Apr.24, 1957 France Apr. 5, 1956 France Aug. 27, 1956 OTHER REFERENCESMcBerty: Fiat Final Report, 774, Anhydrous Chlorides Manufacture, pp.18-20 y( 1946).

1. A METHOD FOR CONTINUOUS, STEADY-STATE PRODUCTION OF ZIRCONIUMTETRACHLORIDE BY THE CHLORINATION OF SOLID BONDED AGGLOMERATES OF:FINELY DIVIDED ZIRCONIUM OXIDEBEARING MATERIAL OF WHICH AT LEAST 80%WILL PASS A 200MESH SCREEN, AND FINELY DIVIDED SOLID CARBONACEOUSREDUCING AGENT OF WHICH AT LEAST 80% WILL PASS A 140-MESH SCREEN, THEAMOUNT OF CARBONACEOUS REDUCING AGENT IN SAID AGGLOMERATES BEINGSTOICHIOMETRICALLY SUFFICIENT TO CONVERT ALL THE OXYGEN IN SAIDZIRCONIUM OXIDE-BEARING MATERIAL TO THE CARBON MONOXIDE/CARBON DIOXIDEMIXTURE PRODUCED UNDER THE EXISTISNG CHLORINATION CONDITIONS, SAIDFINELY DIVIDED ZIRCONIUM OXIDE-BEARING MATERIAL AND SAID FINELY DIVIDEDCARBONACEOUS REDUCING AGENT BEING BONDED TOGETHER WITH AN INORGANICCHEMICAL BINDER OF SUFFICIENT STRENGTH TO PREVENT SUBSTANTIAL PHYSICALDEGRADATION OF THE AGGLOMERATES DURING CHLORATION THEREOF, SAID